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Disappearing During Division

The Golgi complex is an organelle that is generally found in a single copy per cell. How does the parent cell ensure that each daughter receives one? Work over the past decade has shown that the Golgi disassembles early in mitosis and then reassembles toward the end of cell division. This was thought to occur by a process in which the membrane fusion portion of constitutive membrane recycling was inhibited at the beginning of mitosis; continual budding of vesicles from the Golgi would then lead to fragmentation into a cloud of vesicular Golgi remnants that would partition between the daughters passively. However, Zaal et al. suggest that the components of the Golgi complex do not disperse but are actually absorbed into the endoplasmic reticulum (ER). When normal intracellular transport resumes after mitosis, the Golgi is then reassembled. By quantitatively assessing the distribution and mobility of fluorescent proteins and lipids in living cells, they found that Golgi proteins recycled continuously through the ER during interphase and that these proteins accumulated in the ER during mitosis. The apparent lack of distinctive Golgi remnants challenges current ideas on Golgi stability and inheritance, yet the differing results may reflect differences in methodologies, and there may be redundant mechanisms to ensure that no new cell ends up without its Golgi.—SMH